The need of an automatic revolver has always been felt. Fosbery was the first one to modify the revolver of Webley to make it automatic. In the Webley-Fosbery revolver, the body of the weapon is divided in two parts associated by means of sliders and free to move relatively to a certain extent. The upper part of the weapon, which comprises the barrel, cylinder and hammer, in reaction to the shot, moves back with respect of the lower part, which is constituted by the handle and by the trigger support. During this backward motion, the hammer is forced to rotate because its rear part abuts against an inclined plane of the lower part of the body. A lever connected to the hammer acts against the teeth of the drum causing it to rotate. A first drawback of such automatic revolver is that the rotation of the drum occurs at recoil and is consequently violent and can cause damage to parts of the revolver.
An attempt to reduce such inconvenience by inserting a shock absorbing spring between the moving parts has not been successful.
The above inconvenience was overcome by increasing the diameter of the cylinder and by providing the outer portion of the cylinder with zigzag slots adapted to receive a peg associated with the lower part of the body. The action of the peg in the inclined walls of the slots during the backward motion and the return of the upper part of the body causes the rotation of the cylinder. The advantage of a greater strength of this device is however countered by two drawbacks.
A first drawback is that the drum has a considerable size and the second drawback is that it is impossible to rotate the drum without moving the two parts of the firearm. This second drawback is particularly severe. This above described revolver has the following disadvantages.
Stressing and breaking of the lever members undergoing a violent action during the recoil.
In the case of a defective cartridge, it is impossible to take advantage of the typical feature of revolvers that simply allow a pull of the trigger to fire another round.
The firearm must be held firmly in the automatic operation to prevent the transformation of the recoil action into a pitch of the firearm rather than a sliding action of the slider because there is a considerable distance between the axis of the barrel and the rest of the firearm on the hand.
The rotation of the cylinder and the re-cocking of the hammer in the conventional revolvers occur in substantially two ways.
By means of the so-called SA (single action) the hammer is armed by pulling it backwards with the thumb. The index pulls the trigger with a very short stroke (less than 1 mm) to release the hammer.
Shooting DA (double action) with the index finger pulling the trigger with a stroke of about 12 mm arming the hammer, rotating the drum and subsequently firing, with a force on the trigger of about 5 Kg.
In the conventional revolvers both actions are produced by muscular force.